1. Field of the Invention
The present invention relates to thermomechanical analysis (TMA). TMA is a thermal analysis technique in which mechanical properties of a sample of a material are measured as a function of temperature.
2. Background of the Invention
Thermomechanical analysis can be performed using a variety of experimental configurations, including an extension configuration (shown in FIG. 1) and a compression configuration (shown in FIG. 2). Additional configurations for thermomechanical analyzers are well-known to those of skill in the art.
The present invention also relates to Modulated-Temperature DSC (MT-DSC). MT-DSC is a modification of differential scanning calorimetry, in which an oscillating heating rate is superimposed on a conventional linear temperature heating ramp. MT-DSC is described in an article by M. Reading, Trends in Polymer Science., vol. 1, page 248 (1993) and in U.S. Pat. No. 5,224,775 (the "'775 patent", which is incorporated herein by reference). In MT-DSC, the response of the differential heat flow signal (dQ/dt) to the heating rate (dT/dt) is given by: ##EQU1## where C.sub.p is the sample's heat capacity and f(t,T) represents heat flow associated with kinetically limited processes due to physical or chemical changes in the sample that occur both with time and temperature, as explained in Reading's Polymer Science article and disclosed in the '775 patent. The f(t,T) term represents the "non-reversing" heat flow. Thermal events such as crystallization, evaporation, degradation, cross-linking etc. are non-reversing events, that would contribute to the non-reversing term. In MT-DSC the heat capacity of the sample is calculated by deconvoluting the measured heat flow signal into component signals. A sinusoidal temperature modulation is the most commonly applied program, although both saw-tooth and stepwise isothermal programs have been employed.
At present, modulated-temperature programs have only been used in differential scanning calorimeters, although Chen and Dollimore have considered the theoretical implications of using a sinusoidal heating rate in simultaneous DSC-TG (D. Chen and D. Dollimore, Thermochim. Acta, vol. 272, p. 75 (1996)).